AA Batteries: rechargeables or disposables best for me?

After a nasty car accident many years ago when I happened to have a camera with me, I have always carried a film camera in my car. The photos were incredibly useful in refuting the other driver's lies to their insurance company. But having a film camera necessitates changing the film every year or so when it expires.

So, recently I began to think about buying a cheap digital. I chose the Canon A1400 because it has a viewfinder and thus avoids the problem of LCD screens and sunny days. I also liked the fact that it takes AA batteries.

The camera takes one pair to run, so I'm thinking of having one spare pair in the car in the camera bag and a further pair in my handbag. This will mean any temperature problems are taken care of: my handbag doesn't get as hot or as cold as the car can.

So, which type of batteries do I get?

1. Rechargeables, once purchased, are essentially free, however:

I don't know enough about their "shelf" life (= how long a charge lasts), especially when exposed to temperature extremes.

I also wonder about recharging a battery which has simply been sitting there doing nothing since the last charge - I know laptop batteries have a longer total life when cycled regularly as opposed to treating the machine like a desktop computer. I wonder if the total life of the rechargeables will be similarly reduced if I don't pre-drain them before recharging. Rechargeables are more expensive than disposables, so I want them to last as long as possible, since the original aim is to save money.

A further concern is that I assume the "shelf" life declines with age, and how would I know when that started happening and to what extent? I have a voltmeter, but would it tell me anything useful on this score?

2. Disposable alkalines, replaced once a year, ought to work just fine, but that would add to the cost of the overall system and again, the original aim is to save money.

So I figured I would ask you kind folks what you think. This camera system has to work, no matter when, no matter where, but will only need to take say 20-30 photos (though perhaps all with the flash). It will be sitting in the car unused the rest of the time. The car can reach temperatures of -12°C (10° F) overnight and let's say 35-40°C (up to 104°F) during the day. [The camera's operating temps are 0-40°C so unless I'm very unlucky it ought to work in almost all situations.] I accept that the batteries may not be very happy in the cold, that's why I'll have a pair in my handbag to exchange if necessary.

If I go with rechargeables, making sure they are recharged on a frequent-enough basis is not a problem -- I already have many repeating tasks on varying schedules. But I have to be sure that with three pairs of batteries, I will get the photos I need. And I don't want to have to replace rechargeables for a good while.

What do you folks think? Is buying rechargeables going to do what I need in this system?